Touch screens, including capacitive touch screens, are commonly used to input information into a variety of devices, including, for example, smart phones, automated teller machines (ATMs), laboratory equipment, drawing capture devices, and the like. Touch screens may be used with a variety of tools to indicate a two-dimensional position on the touch screen. For example, position on a touch screen may be indicated by a finger, a variety of stylus-like devices, and the like, making contact with a touch screen. It is appreciated that such tools are not necessarily required to contact the touch screen, and that such tools may indicate information to the touch screen in addition to position, for example, such tools may indicate a pressure level.
It may be useful to determine a particular tool being used with a touch screen, from among a plurality of possible tools. For example, it may be useful to differentiate between a finger and a particular stylus device. In addition, it may be useful to differentiate among a number of different stylus devices. It is also useful to differentiate between “intended use” tools, e.g., fingers and styli, and other objects that may make “unwanted” contact with a touch screen, e.g., a palm or a side of a hand.
Based upon such differentiation, different actions may be taken based upon a particular tool in use. For example, use of a first stylus with a touch screen may indicate that a particular display region is filled with a first color, while use of a second stylus with the touch screen may indicate that a particular display region is filled with a second color. As another example, use of a finger with a touch screen may indicate a menu entry, while use of a stylus device with the touch screen may indicate entry of graphical information. As a further example, in a graphical application, input information from a stylus may be considered pertinent and used by the application, while input information from a finger, or hand, may be considered extraneous, and discarded. As a yet further example, touch input from a stylus may be accepted while a touch input from the side of a hand, occurring simultaneously with the stylus touch, may be ignored.